An ongoing problem in the area of lubricating machinery is improving the lubricants ability to prevent metal-on-metal contact. Previously, phosphorus esters were used, often in combination with other additives, to provide antiwear and extreme pressure protection to lubricants. Additionally, today the design of equipment has forced the operation temperatures into higher regions. These increased temperatures in combination with oxygen may oxidize the lubricant. It would be advantageous to have additives which improve the antiwear and extreme pressure protection of the lubricant while also providing good antioxidation protection.
U.S. Pat. No. 2,905,683, issued to Goldsmith, relates to ether containing esters of dithiophosphoric acids and salts thereof. The dithiophosphric acid esters have ether containing radicals.
U.S. Pat. No. 3,214,423, issued to Zech et al, relates to thiophosphates of polyoxyethylene compounds. The thiophosphates are derived from the reaction of polyoxyethylene derivatives of fatty alcohols, fatty amines, fatty amides, fatty acids, hydroxy esters of fatty acids and alkyl phenols having from about 8 to about 18 carbon atoms in the alkyl chain. The thiophosphates are water soluble and are useful as an aqueous coolant for metal cutting.
U.S. Pat. No. 4,044,032, issued to Wiley et al, relates to metal dialkyl dithiophosphates. The dialkyldithiophosphates are prepared from oxyalkylated long straight chain alcohols, acid, and mercaptans. These materials are useful in lubricants such as automatic transmission fluids.
U.S. Pat. No. 4,579,672, issued to Brecker et al, relates to functional fluids and lubricants with improved water tolerance by including alkoxypolyethyleneoxy acid phosphite ester additives.
U.S. Pat. No. 5,342,531, issued Walters et al, relates to polyalkylene glycol lubricants compositions. The lubricants include (a) sulfur containing antiwear or extreme pressure agent, (b) an amine salt of a partially esterified monothiophosphoric acid, and (c) an amine salt of a partially esterified phosphoric acid.